Check engine light question
10-28-2006, 05:57 PM
#2
Team Owner
Originally Posted by ransvett
Well the check engine light came on for the first time today. What now? Do I have to take it to the dealer? help please
http://97vette.com/howto/codes/index.html
Then post back with what you find for codes. We'll get you set straight.
Paul
10-28-2006, 06:37 PM
#3
Originally Posted by ransvett
Well the check engine light came on for the first time today. What now? Do I have to take it to the dealer? help please
Check to see if the gas cap is on tightly.
10-28-2006, 08:55 PM
#7
Team Owner
Originally Posted by ransvett
sorry I forgot to mention its an 02 zo6
You can just wait and the computer will display them and cycle thru them automatically. Otherwise you can get into the manual mode by pressing the 2 or the 3 key on the DIC and you can cycle thru them by pressing the buttons. When you are done, press reset. If it is only a PCM code it is not likely fatal.
Last edited by talon90; 10-28-2006 at 08:59 PM.
10-28-2006, 10:47 PM
#9
Le Mans Master
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CI 7-8 Veteran
St. Jude Donor '03-'04-'05
Originally Posted by georgec114
Check to see if the gas cap is on tightly.
10-28-2006, 11:53 PM
#10
Racer
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Here are the codes
P0171-H
P0174-H I hit the reset button and now check engine light is off. What do these codes mean Fuel trim system lean bank 1 and 2 What the heck is that??
P0171-H
P0174-H I hit the reset button and now check engine light is off. What do these codes mean Fuel trim system lean bank 1 and 2 What the heck is that??
10-29-2006, 12:26 AM
#11
Le Mans Master
Check to see if the MAF is dirty, possibly from an over-oiled air filter or something similar, or also possibly an air leak in the intake after the MAF. If the MAF is dirty, clean the wires with electrical contact cleaner.
10-29-2006, 12:50 AM
#13
Race Director
Originally Posted by ransvett
sorry I forgot to mention its an 02 zo6
10-29-2006, 01:04 AM
#14
Racer
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after market its been on the car for 3 years and never a problem though its the Halltech sidewinder. I thought that A code with a H after it means there is no longer a problem? I guess im gonna have to go drive it tommorrow and see if it throws the code again huh?
10-29-2006, 01:11 AM
#15
Race Director
From the desk of Jim Hall:
That will not happen with lean codes, unless you have a major air leak somewhere.
This type of code happens as a result of the screenless MAF sensor, which is a poor air meter without the laminar screen.
At low rpm, the airflow going into the MAF is more turbulent due to the throttle plate being mostly shut, causing some air to be missed by the MAF and subsequently measured at the O2 sensors instead.
The difference between the measured air at the MAF and the actual Oxygen left over at the O2 sensor creates longer fuel trims to make up for the new measurement. This creates a long term trim in that particular fuel cell, which if 24% is reached (easy to do without a screen) the codes you mentioned pop.
You can reset the PCM, but better yet, pull the negative side of the battery all night to reset the LTFs.
This should solve the problem.
If they come back, you can install the 2001 Z06 MAF sensor, or reprogram your PCM for the LTF problem.
THIS CONDITION WILL NOT BURN PISTONS!
Another option is to go back to the stock setup, but the former recommendations should be tried first.
This condition is never reported in the LS1, or 2001 Z06, since the MAF used has the proper laminar screen in place. Just like a wind tunnel laminar screen.
I understand that the 2005 LS2 will be going back to the laminar airflow screen as well.
Jim Hall
That will not happen with lean codes, unless you have a major air leak somewhere.
This type of code happens as a result of the screenless MAF sensor, which is a poor air meter without the laminar screen.
At low rpm, the airflow going into the MAF is more turbulent due to the throttle plate being mostly shut, causing some air to be missed by the MAF and subsequently measured at the O2 sensors instead.
The difference between the measured air at the MAF and the actual Oxygen left over at the O2 sensor creates longer fuel trims to make up for the new measurement. This creates a long term trim in that particular fuel cell, which if 24% is reached (easy to do without a screen) the codes you mentioned pop.
You can reset the PCM, but better yet, pull the negative side of the battery all night to reset the LTFs.
This should solve the problem.
If they come back, you can install the 2001 Z06 MAF sensor, or reprogram your PCM for the LTF problem.
THIS CONDITION WILL NOT BURN PISTONS!
Another option is to go back to the stock setup, but the former recommendations should be tried first.
This condition is never reported in the LS1, or 2001 Z06, since the MAF used has the proper laminar screen in place. Just like a wind tunnel laminar screen.
I understand that the 2005 LS2 will be going back to the laminar airflow screen as well.
Jim Hall
10-29-2006, 01:20 AM
#16
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Man Im so far away from understanding any of that. Im just not that smart about this stuff in simple terms do I have to worry about damage to my car? I tell ya I soooo appreciate all your guys help this is the best site ever!!
10-29-2006, 01:28 AM
#17
Le Mans Master
Originally Posted by ransvett
Man Im so far away from understanding any of that. Im just not that smart about this stuff in simple terms do I have to worry about damage to my car? I tell ya I soooo appreciate all your guys help this is the best site ever!!
Last edited by ZeeOSix; 10-29-2006 at 01:30 AM.
10-29-2006, 01:29 AM
#18
Race Director
I think this sums it up nicely:
If they come back, you can install the 2001 Z06 MAF sensor, or reprogram your PCM for the LTF problem.
THIS CONDITION WILL NOT BURN PISTONS!
The MAF (Mass Air Flow) sensor is connected to your air filter. 2001 Z06s and all Coupes and verts have a wire mesh screen ahead of the MAF sensor wires. This smooths out the flow of airthrough the MAF. A 2001 Z06 MAF has the screen, so if you can install one of those, your code should not come back.
If they come back, you can install the 2001 Z06 MAF sensor, or reprogram your PCM for the LTF problem.
THIS CONDITION WILL NOT BURN PISTONS!
The MAF (Mass Air Flow) sensor is connected to your air filter. 2001 Z06s and all Coupes and verts have a wire mesh screen ahead of the MAF sensor wires. This smooths out the flow of airthrough the MAF. A 2001 Z06 MAF has the screen, so if you can install one of those, your code should not come back.
10-29-2006, 02:39 AM
#19
Tech Contributor
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Know you have some trouble with the technical terms but they really aren't bad once you get used to them. Your problem could be several things including what this 2004 Bulletin covered:
97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (Jul 12, 2004)
97 - 05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires On One Bank.
The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.
Condition/Concern:
Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.
Recommendation/Instructions:
If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:
Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.
Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.
Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.
Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
The following diagnostic procedure is in the Service Manual for the two codes you see. It requires the use of a scan tool to do some of the checks but should give you some idea where to look for problems. Some of these items could be covered under your emissions warranty as long as you do not have any aftermarket equipment causing the problem.
DTC P0171 or P0174
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.
Conditions for Running the DTC
DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
The intake air temperature (IAT) is between -20 and +90°C (4-194°F).
The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
The vehicle speed is less than 137 km/h (85 mph).
The engine speed is between 400-3,000 RPM.
The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
The mass airflow (MAF) is between 5-90 g/s.
The fuel level is more than 10 percent.
The throttle position (TP) is less than 90 percent.
Conditions for Setting the DTC
The average long term fuel trim cell value is above 23 percent.
All of the above conditions are present for 6 seconds.
Diagnostic Aids
The system will go lean if an injector is not supplying enough fuel.
A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.
Use a scan tool in order to review the Failure Records . If an intermittent condition is suspected, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
If the conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.
Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
If any DTCs other than P0171 or P0174 are set, refer to those DTCs before continuing
Install a scan tool.
Start and idle the engine at the normal operating temperature in closed loop.
Record the Long Term Fuel Trim.
Turn OFF the engine.
Turn ON the ignition, with the engine OFF.
Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the long term fuel trim is greater than the specified value?
23%
Go to Step 3
Go to Diagnostic Aids
3
Operate the engine at idle.
Observe the HO2S parameter with a scan tool.
Does the scan tool indicate that the parameter is within the specified range and fluctuating?
200- 800 mv
Go to Step 4
Go to Step 5
4
Turn OFF the engine.
Visually and physically inspect the following items:
The vacuum hoses for splits, kinks, and proper connections. Refer to Emission Hose Routing Diagram .
Ensure that the vehicle has sufficient fuel in the tank. If the fuel pressure is too low this DTC may set. Refer to Fuel System Diagnosis .
Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Did you find and correct the condition ?
--
Go to Step 7
Go to Step 6
5
Turn OFF the engine.
Check the HO2S for proper installation.
Ensure that the electrical connectors and the wires are secure and not contacting the exhaust system.
Check for a short between the signal circuit and the low reference circuit.
Did you find and correct the condition?
--
Go to Step 7
Go to Fuel System Diagnosis
6
Operate the engine at idle.
Check for any missing, loose, or leaking exhaust components forward of the HO2S.
Check for vacuum leaks at the intake manifold, throttle body, and injector O-rings.
Check the air induction system and the air intake ducts for leaks.
Check the AIR system for leaks, improper air delivery, and for the shut-off valves not closing.
Check the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.
Did you find and correct the condition?
--
Go to Step 7
Go to Symptoms - Engine Mechanical in Engine Mechanical
7
Important
After any of the above repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 8
Go to Step 2
8
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
Bill
97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (Jul 12, 2004)
97 - 05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires On One Bank.
The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.
Condition/Concern:
Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.
Recommendation/Instructions:
If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:
Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.
Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.
Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.
Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
The following diagnostic procedure is in the Service Manual for the two codes you see. It requires the use of a scan tool to do some of the checks but should give you some idea where to look for problems. Some of these items could be covered under your emissions warranty as long as you do not have any aftermarket equipment causing the problem.
DTC P0171 or P0174
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.
Conditions for Running the DTC
DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
The intake air temperature (IAT) is between -20 and +90°C (4-194°F).
The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
The vehicle speed is less than 137 km/h (85 mph).
The engine speed is between 400-3,000 RPM.
The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
The mass airflow (MAF) is between 5-90 g/s.
The fuel level is more than 10 percent.
The throttle position (TP) is less than 90 percent.
Conditions for Setting the DTC
The average long term fuel trim cell value is above 23 percent.
All of the above conditions are present for 6 seconds.
Diagnostic Aids
The system will go lean if an injector is not supplying enough fuel.
A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.
Use a scan tool in order to review the Failure Records . If an intermittent condition is suspected, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
If the conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.
Step
Action
Values
Yes
No
1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls
2
Important
If any DTCs other than P0171 or P0174 are set, refer to those DTCs before continuing
Install a scan tool.
Start and idle the engine at the normal operating temperature in closed loop.
Record the Long Term Fuel Trim.
Turn OFF the engine.
Turn ON the ignition, with the engine OFF.
Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the long term fuel trim is greater than the specified value?
23%
Go to Step 3
Go to Diagnostic Aids
3
Operate the engine at idle.
Observe the HO2S parameter with a scan tool.
Does the scan tool indicate that the parameter is within the specified range and fluctuating?
200- 800 mv
Go to Step 4
Go to Step 5
4
Turn OFF the engine.
Visually and physically inspect the following items:
The vacuum hoses for splits, kinks, and proper connections. Refer to Emission Hose Routing Diagram .
Ensure that the vehicle has sufficient fuel in the tank. If the fuel pressure is too low this DTC may set. Refer to Fuel System Diagnosis .
Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Did you find and correct the condition ?
--
Go to Step 7
Go to Step 6
5
Turn OFF the engine.
Check the HO2S for proper installation.
Ensure that the electrical connectors and the wires are secure and not contacting the exhaust system.
Check for a short between the signal circuit and the low reference circuit.
Did you find and correct the condition?
--
Go to Step 7
Go to Fuel System Diagnosis
6
Operate the engine at idle.
Check for any missing, loose, or leaking exhaust components forward of the HO2S.
Check for vacuum leaks at the intake manifold, throttle body, and injector O-rings.
Check the air induction system and the air intake ducts for leaks.
Check the AIR system for leaks, improper air delivery, and for the shut-off valves not closing.
Check the crankcase ventilation system for leaks. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.
Did you find and correct the condition?
--
Go to Step 7
Go to Symptoms - Engine Mechanical in Engine Mechanical
7
Important
After any of the above repairs, use the scan tool Fuel Trim Reset function in order to reset the Long Term Fuel Trim.
Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.
Does the DTC run and pass?
--
Go to Step 8
Go to Step 2
8
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK
Bill
